The present invention relates generally to a furniture veneer and method of making same, and, more particularly, to a common wood veneer having a surface imitating that of a prized wood, and a method of making same.
The truly prized woods, such as nut burl, olive burl, myrtle burl and the like, are not only very expensive, but very difficult to find on the market. In addition, the true burl has small and irregular sizes and exhibits holes and other defects. Therefore, when veneer sheets are obtained therefrom, scraps on the order of 30-40% occur, and the manufacturing process is more complicated and expensive than in the case of the common wood veneers. Accordingly, the cost of finished burl veneer--both in terms of material and manufacturing--is almost prohibitively high.
For these reasons, various attempts have been made to obtain veneers made from common wood (e.g., birch of African nut), but having a surface imitating that of a prized wood (e.g., a burl). The various attempts have not proven entirely satisfactory, however, as they require a rather complex manufacturing procedure and result in an imitation having such a low degree of definition that, even without a too accurate inspection, it is easily noted as only an imitation. Generally, these attempts have utilized a transfer picture (decalcomania) reproducing the wood grain design appearance of the prized wood to be imitated, the transfer picture being applied to the surface of a veneer of common wood by means of a hot press. Much of the difficulty encountered out arises of the nature of the common wood veneers. The wood veneers are typically 0.6-0.7 millimeters thick, composed of hard longitudinal fibers and soft pulp, with a rough surface. Very often one part of the veneer is more porous or thicker or softer than the remainder. Many veneers are corrugated, resulting in the uneven absorption of humidity. Thus, in the hot stamping process the veneer's rough wood surface, its irregular thickness, its irregular hardness and its corrugated surface cause the formation of unacceptable longitudinal creases (when a hot roll press is used) or bubbles (when a hot platen press is used) as a result of thermoplastic flow in the heat-softened surface of the hot stamping foil, thereby distorting the image of the prized wood to be imparted to the common wood veneer.
More particularly, in the hot roll press process, the silicone rolls are at a temperature (160.degree.-180.degree. C.) sufficient to cause the carrier film of the hot stamping foil to approach its melting point and soften. Thus, the hot roll tends to press the softened carrier film into the soft pulp between the hard fiber ribs of the veneer, thus creating the longitudinal creases found in approximately 40% of the veneers formed by this process. In the hot platen press process, the hot expanding air from the heated pores of the thermoplastic layer of the wood surface gives rise to bubbles, which are typically unable to escape from the two surfaces under pressure (that is, the thermoplastic layer of the wood surface and the foil). This is a severe problem when large surfaces are involved (for example, 700.times.260 cm), although a much lesser or even insignificant problem where the foil surface has at least one dimension so small as to enable any potential bubbles to escape from between the two surfaces. A further deficiency of the hot roll press process is that, despite use of a low production speed (for example, three meters per minute), the contact time of the hot rolls with the laminate is too short with resultant poor adhesion and poor abrasion resistance of the transfer.
Indeed, as illustrated in U.S. Pat. No. 1,893,384, the heretofore unavoidable distortions in a transferred picture due to the direct contact with the structure and grain of the common wood veneer have led to transfer systems in which a smoothed and pasted wood surface is completely covered by an aqueous transfer picture which hides from view the natural wood structure. The process, however, leaves the picture surface so highly water-sensitive that it cannot be cleaned with water-containing cleaners, becomes sticky in high humidity, and generally is not adapted for use on furniture. Similarly, U.S. Pat. No. 4,125,655 describes small plaques which are formed by applying a hot stamping foil (7/8 inch wide) under localized heat and pressure to a smooth decorative thermoplastic film (such as Mylar) laminated on a plastic plate readily deformable by moderate heat and pressure. The foil is so narrow that potential bubbles are able to escape from under the foil without becoming trapped.
While some creasing or bubbling of the heat softened surface of the hot stamping foil may be acceptable in certain applications involving non-discriminating purchasers and may even produce relatively satisfactory products where the veneer is of such small dimensions that the imperfections caused by the creases and bubbles may be trimmed away (for example, in the manufacture of such small items as plaques), in the furniture industry, all purchasers are extremely discriminating and the veneer applications are so extensive in area as to make the trimming solution impractical.
Wood is practically non-thermoplastic and relatively insensible within limits to water, steams, heat and solvents. Accordingly, there are instances where the hot stamping foils do not stamp (i.e., do not leave the color transfer) on the wood or, if they do stamp, the poor adhesion of the transfer to the wood provides a very low level of resistance to abrasion, scratching, etc. While many applications will not require the various resistances and strengths achieved by adequate adhesion of the transfer to the wood, in the furniture industry such resistances and strengths are critical both during the manufacturing process and thereafter. For example, resistance to hot water and steam is essential when the veneer will be pressed in a platen press (typically for 80 seconds at 110.degree. C.) when glued to a substrate using aqueous-reactive glues such as urea, urea melanine, or the like. Resistance to solvents--e.g., immersion in a solvent such as ethyl acetate for two minutes--is essential when the veneer is to be glued to a substrate (such as a chip board) with solvent glues or washed with solvents or lacquered during the furniture manufacturing process. Resistance to heat and humidity is also critical when the furniture is to be used in tropical countries where humidities of 95% and temperatures of 45.degree. C. may be encountered. Indeed, under transport in enclosed containers, similar humidities and temperatures up to even 80.degree. C. may be encountered. Resistance to immersion in water is also critical where the furniture may be exposed to rain during transport or other circumstances. And, of course, the veneer must be resistant to the oils found naturally in the wood or solvents applied during maintenance of the furniture (for example, during polishing). Finally, all this must be accomplished in a veneer of substantial size (e.g., up to 700.times.260 centimeters), while permitting the natural wood structure of the veneer to remain visible. Accordingly, it is an object of the present invention to provide a veneer of common wood having a surface imitating that of a prized wood.
Another object is to provide such a veneer having a transfer surface devoid of imperfections caused by creases or bubbles in the heat-softened surface of the stamping foil.
A further object is to provide such a veneer exhibiting a strong adhesion of the transfer to the wood so that the final product is marked by a high level of resistance to abrasion, heat, solvents, water, steam, oils and the like.
It is also an object of the present invention to provide a veneer suitable for use in the furniture industry.
It is a further object to provide a method for producing such a veneer.